1,4-Dioxane is a probable human carcinogen and commonly detected groundwater contaminant in Long Island, NY. Data from Unregulated Contaminant Monitoring Rules (UCMR) 3 revealed that 1,4-dioxane was detected in 33 of 36 public water systems in Long Island, with the highest detected concentration (33 μg/L) in the nation. Advanced oxidation processes (AOP) have been proven to be effective for 1,4-dioxane degradation and have been successfully applied for 1,4-dioxane remediation. An emerging challenge for the application of AOP (e.g. UV/H2O2) is the generation of degradation byproducts that may (i) boost heterotrophic bacteria growth in the distribution systems, (ii) serve as precursors of disinfection byproducts, and (iii) exert toxicity similar to the target contaminant. In addition, the high residue of H2O2 (up to 10 mg/L) in the AOP effluent exerts a chlorine demand that could potentially weaken the disinfection effect. In this research, the performance of a lab-scale granular activated carbon (GAC) filter following UV/H2O2 system was evaluated for removal of 1,4-dioxane byproducts and residual H2O2. The objectives of this study are to (i) investigate the interactions between 1,4-dioxane byproducts (formic acid, acetic acid, formaldehyde and glyoxal) adsorption and H2O2 quenching for different types of GAC, (ii) determine the influence of water quality and operating parameters on GAC column performance. Batch adsorption experiments of byproducts as single- or multi- component mixture (equimolar concentration of all byproducts) onto GAC at different concentrations were tested with 3 initial H2O2 levels (0, 1 and 5 mg/L), and the design of rapid small-scale column tests (RSSCTs) is ongoing to evaluate the GAC column performance. Preliminary data showed that in presence of 0.5 g/L F-600 GAC, 10 mg/L of H2O2 decomposed within 50 hours. For the 3-day batch experiments, the presence of 5 mg/L H2O2 showed little effect on the intermediates adsorption for both single- and multi-component solutions. The maximum adsorption capacities for single component solutions calculated by the Langmuir isotherm equation were 66.9 mg/g GAC for formic acid and 21.4 mg/g GAC for acetic acid, and competitive adsorption was observed between these two intermediates (17.6 mg/g GAC and 8.5 mg/g GAC respectively for formic and acetic acid in multi-component solution). GAC adsorption was not effective in removal of formaldehyde and glyoxal under the experimental conditions tested.

Evaluation of granular activated carbon performance to remove 1,4-dioxane degradation byproducts and residual H2O2 from UV/H2O2 treatment system

2019 Spring National Meeting

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